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    <h1 id="sel4-001-rt-dev">seL4 0.0.1-rt-dev</h1>

<p>The development branch of the for the seL4 realtime extensions. This
branch is not verified and is under active development.</p>

<h2 id="highlights">Highlights</h2>

<ul>
  <li>
    <p>Maximum priorities</p>

    <ul>
      <li>Previously seL4 would not allow threads to set any other
thread’s priority to higher than its own. This has been
extracted into a separate field for the RT kernel, a maximum
priority, which limits what thread cans set their own or other
threads priorities to.</li>
    </ul>
  </li>
  <li>
    <p>Scheduling contexts</p>

    <ul>
      <li>This branch adds scheduling contexts to seL4, which represent
CPU time. Scheduling contexts are separate to threads
(although threads required one to run) and can be passed
around over IPC.</li>
      <li>Scheduling contexts allow developers to create periodic
threads, temporally isolation threads and have variable
timeslices for round robin threads.</li>
    </ul>
  </li>
</ul>

<p>For more details, please see the manual. Most of the updates are in the
threads chapter.</p>

<h2 id="api-changes">API Changes</h2>

<ul>
  <li><code class="language-plaintext highlighter-rouge">seL4_TCB_Configure</code> arguments changed (domain removed, scheduling
    context cap and max priority added).</li>
</ul>

<h2 id="api-additions">API Additions</h2>

<ul>
  <li><code class="language-plaintext highlighter-rouge">seL4_CapSchedControl</code> - initial cap for control of CPU time</li>
  <li><code class="language-plaintext highlighter-rouge">seL4_SchedContextObject</code> - new object for that allows threads
    access to CPU time</li>
  <li><code class="language-plaintext highlighter-rouge">seL4_SchedContextBits</code> - size in bits of a scheduling context
    object</li>
  <li><code class="language-plaintext highlighter-rouge">seL4_NBSendRecv</code> - new system call which allows once kernel
    invocation to perform a non-blocking send on one capability, and
    wait on another.</li>
  <li><code class="language-plaintext highlighter-rouge">seL4_NBSendRecvWithMRs</code> - uses above new system call without
    touching the IPC buffer, passing only data in registers</li>
  <li><code class="language-plaintext highlighter-rouge">seL4_Time</code> - type for specifying temporal units to the kernel</li>
  <li><code class="language-plaintext highlighter-rouge">seL4_TCB_SetMaxPriority</code> - set the max priority for a tcb,
    threads can only start / set priorities threads up to and
    including their max priority</li>
  <li><code class="language-plaintext highlighter-rouge">seL4_Prio_t</code> - type for priority and max priority, used in
    <code class="language-plaintext highlighter-rouge">TCB_Configure</code></li>
  <li><code class="language-plaintext highlighter-rouge">seL4_CNode_SaveTCBCaller</code> - save the reply cap of the target tcb.
    This allows another thread to reply on behalf of the owner of the
    reply cap.</li>
  <li><code class="language-plaintext highlighter-rouge">seL4_SchedControl_Configure</code> - invokes the scheduling control cap
    to populate a scheduling context with parameters</li>
  <li><code class="language-plaintext highlighter-rouge">seL4_SchedContext_Yield</code> - end the timeslice of the thread bound
    to the sched context invoked.</li>
  <li><code class="language-plaintext highlighter-rouge">seL4_SchedContext_BindTCB</code> - bind a tcb to a scheduling context,
    if the TCB is runnable and scheduling context has budget, this
    will start the tcb running</li>
  <li><code class="language-plaintext highlighter-rouge">seL4_SchedContext_UnbindTCB</code> - remove binding of a scheduling
    context from a tcb, tcb will no longer run but state will be
    preserved</li>
  <li><code class="language-plaintext highlighter-rouge">seL4_CapInitThreadSC</code> - capability to the initial threads
    scheduling context</li>
  <li><code class="language-plaintext highlighter-rouge">seL4_CapSchedControl</code> - scheduling control capability, which is
    given to the root thread</li>
  <li><code class="language-plaintext highlighter-rouge">seL4_SchedContext_BindNotification</code> - Bind a notification to a
    scheduling context. Passive threads waiting on this notification
    will borrow the scheduling context.</li>
  <li><code class="language-plaintext highlighter-rouge">seL4_SchedContext_UnbindNotification</code> - unbind the notification.</li>
</ul>

<h2 id="api-deletions">API deletions</h2>

<ul>
  <li><code class="language-plaintext highlighter-rouge">seL4_Yield</code> (replaced by <code class="language-plaintext highlighter-rouge">seL4_SchedContext_Yield</code>)</li>
  <li><code class="language-plaintext highlighter-rouge">seL4_DomainSet</code></li>
  <li>Domain scheduler removed.</li>
</ul>

<h2 id="library--test-compatability">Library &amp; test compatability</h2>

<p>The ‘rt’ branch of <code class="language-plaintext highlighter-rouge">seL4_libs</code> has been adapted to the rt branch of seL4,
and the rt branch of sel4test has been ported to the <code class="language-plaintext highlighter-rouge">seL4_rt-dev-0.0.1</code>
kernel, along with many more tests written suited to the rt kernel. To
run it, checkout the <code class="language-plaintext highlighter-rouge">default.xml</code> manifest on the rt branch of
sel4test-manifest.</p>

<p>The rt branch is in no way compatible with the master branch of seL4.</p>

<p>More details See the <code class="language-plaintext highlighter-rouge">0.0.1-rt-dev</code> manual included in the release.</p>


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